This invention relates generally to a heat sealing machine and in particular to a new and novel battery heat sealing machine.
Automotive battery shells or containers, until the 1960's traditionally were made of a rubber composition and contained a top cover over each cell in the battery. The multi-cover top cover then evolved into a one-piece cover which covered all the battery cells at once. In later batteries, the one-piece top cover was sealed with an epoxy glue to the lower battery container.
Various machines were designed during this time to assemble the various battery components, such as battery plates and separators, together into a complete battery. Several such machines are shown in the U.S. Pat. No. 1,932,136, issued on Oct. 24, 1933 to W. W. Hole and in the U.S. Pat. No. 2,324,523, issued on Jul. 20, 1943 to A. D. Lund. Later developed assembling machines are shown in the U.S. Pat. No. 4,507,856, issued to E. J. Pearson on Apr. 2, 1985 and in the U.S. Pat. No. 4,509,252, issued to A. Sabatino et al on Apr. 9, 1985.
During the 1960's, battery containers were introduced to the market with the container being made of a copolymer of propylene and ethylene and other constituents. The copolymer container was lighter in weight than the rubber container and had thin walls. This construction permitted larger internal dimensions for a given outside dimension of the container. Another improved feature of the copolymer container was that it had a better impact resistance than the previous rubber container.
The sealing of batteries during this period and in the early 1970's took many forms as typified by the U.S. Pat. No. 3,427,205, issued on Feb. 11, 1969 to K. F. Plitt et al and in the U.S. Pat. No. 3,544,383, issued on Dec. 1, 1970 to J. E. Oltman. Another approach to battery sealing of the top cover is shown in the U.S. Pat. No. 3,629,010, issued to L. W. Hahn on Dec. 21, 1971 which uses a low viscosity sealant material. In addition, machines were soon developed to automatically install the covers on the battery container as shown in the U.S. Pat. No. 4,306,355, issued to S. Hawrylo et al on Dec. 22, 1981.
Development of other advantageous construction arts followed after the change to the copolymer composition for the battery container. Included in these developments were (1) thru-the-partition connections and (2) heat seal bonding of the top cover to the battery container. The thru-the-partition connection is a connection between adjacent battery cells through a hole in the partition wall that divides the cell enclosures. This type connection eliminated obstructions to the entire top of the container after which it became possible to heat seal the top cover to the battery container by heating the mating surfaces of the top cover and the upper periphery and partitions of the battery container.
The heat seal bonding technique required the heating of the top cover and the upper portions of the battery periphery and the partitions to a softened or near liquid state. After this, the mating parts were placed together with just the right pressure to bond the two pieces together. The seal was accomplished within seconds and the use of epoxy glue, with its accompanying worker health problems, was eliminated. In addition, the additional expense and cleanup problems associated with epoxy glue was also eliminated.
Heat sealing quickly became the dominate sealing method in the battery industry and the device or machine used to heat and melt the mating surfaces and to seal them together is known as a "Heat Seal Machine" in the battery industry. These machines have been commonly used in the industry for about the last two decades starting in the early 1970's and running through the 1980's to the present.
An example of a fusion or thermo bonding is shown in the machine typified by the U.S. Pat. No. 3,909,301, issued on Sep. 30, 1975 to R. L. Schenk, Jr. and in the U.S. Pat. No. 3,909,300, issued to R. L. Schenk, Jr. et al on the same date. A further example of these types of heat sealing machines is the U.S. Pat. No. 3,908,743, issued to R. L. Schenk, Jr. et al on Sep. 30, 1975 and the U.S. Pat. No. 3,908,738, issued to J. A. Bruzas et al on the same date.
Later developments in battery sealing of various parts of the battery are shown in the U.S. Pat. No. 4,091,189, issued to A. Farwer et al on May 23, 1978 and in the U.S. Pat. No. 4,186,246, issued on Jan. 29, 1980 to R. K. Sugalski. In a similar manner, the U.S. Pat. No. 4,252,873, issued to J. Epstein et al on Feb. 24, 1981 and the U.S. Pat. No. 4,308,323, issued to B. Bowsky on Dec. 29, 1981, teach further efforts at improving sealing in a battery. A universal seal for use in a lithium battery is shown in the U.S. Pat. No. 4,603,095, issued to B. Bowsky on Jul. 29, 1986 and a further type of battery seal is shown in the U.S. Pat. No. 4,567,121, issued on Jan. 28, 1986 to A. Gilmour. A cylindrical storage cell seal is shown in the U.S. Pat. No. 4,656,736, issued on Apr. 14, 1987 to N. Volkhin et al.
As inventions in heat seal bonding developed, continuous machines emerged such as the rotary device shown in the U.S. Pat. No. 3,873,400, issued to T. Tsuchida et al on Mar. 25, 1975 and the rotary machine shown in the U.S. Pat. No. 4,502,213, issued on Mar. 5, 1985 to J. A. Madden et al. Other types of improved heat seal machines were developed, in the early 1980's, as shown in the U.S. Pat. No. 4,221,626, issued on Sep. 9, 1980 to B. J. Clay and in the U.S. Pat. No. 4,310,376, issued on Jan. 12, 1982 to R. Ebina et al. Separate heaters were tried in the U.S. Pat. No. 4,525,923, issued Jul. 2, 1985 to O. E. Alvarez and opposing pivoted platen structures was attempted in the U.S. Pat. No. 4,596,625, issued on Jun. 24, 1986 to the same inventor.
The introduction of copolymer battery containers during the 1960's also resulted in later machine developments centered around heating of the mating components. The use of a single heating element for both the top cover and the battery container was attempted as early as Apr. 29, 1969 as shown in the U.S. Pat. No. 3,441,448, issued to B. P. Hayward et al on that date. This patent on a single station device did not disclose details on the heater but emphasized the use of different forces to complete sealing and the use of separate heaters for the mating surfaces. While these patents illustrate the early attempts at heat sealing, they also show the lack of knowledge of the problems to be encountered with heat seal bonding when using heated platens. Early designs of platens used multi-piece platens with two separate heat conducting surfaces which were attached to the heater plate.
During extended use of the platen, a corrosion would occur between the separate pieces of the platen or the separate pieces would warp with repeated heating and cooling. As a result, the uniform transfer of heat was inhibited and/or the even melt of the top cover on the battery container top surface would be effected because of the warp. Compensation for warp of the separate pieces of the platen in an attempt to obtain uniform heat transfer resulted in various complicated mechanisms in the heat seal machine such as shown in the U.S. Pat. No. 3,627,617, issued to E. G. Schaumburg on Dec. 14, 1971 and in the U.S. Pat. No. 3,686,056, issued on Aug. 22, 1972 to R. M. Fiandt.
Other heating platen designs have been tried such as using platens of three levels which are common today. These consist of the center piece containing the electric heating elements with a top and bottom sub-platen made to contour to the top cover and the battery container respectively. The top and bottom sub-platens of this design transfer heat from the center piece. However continual usage of this type of a three-piece platen causes warpage and/or corrosion between the pieces and the heat transfer in the platen becomes uneven.
Comb shaped heating devices such as taught in the U.S. Pat. No. 3,778,314, issued on Dec. 11, 1973 to S. Kano et al, have even been tried along with infrared heating, such as shown in the U.S. Pat. No. 3,883,369, issued on May 13, 1975 to J. P. Badger et al in order to overcome problems in heating and softening the mating pieces on the battery.